Figure 2.21: Comparison
of warm-season (Jones et al., 1998) and annual mean (Mann et al., 1998, 1999)
multi-proxy-based and warm season tree-ring-based (Briffa, 2000) millennial Northern
Hemisphere temperature reconstructions. The recent instrumental annual mean Northern
Hemisphere temperature record to 1999 is shown for comparison. Also shown is an
extra-tropical sampling of the Mann et al. (1999) temperature pattern reconstructions
more directly comparable in its latitudinal sampling to the Jones et al. series.
The self-consistently estimated two standard error limits (shaded region) for
the smoothed Mann et al. (1999) series are shown. The horizontal zero line denotes
the 1961 to 1990 reference period mean temperature. All series were smoothed with
a 40-year Hamming-weights lowpass filter, with boundary constraints imposed by
padding the series with its mean values during the first and last 25 years.